Summary of work: Unnecessary morbidity and mortality are important problems which lead to increased health-care costs and can ultimately result in premature death. It has been estimated that approximately two-thirds of mortality is due to potentially preventable causes - 1.2 million deaths (65%) and 8.4 million years of life lost before age 65 (63%). Principal factors associated with unnecessary morbidity and mortality include tobacco use, high blood pressure, improper nutrition, lack of screening and prevention services, alcohol abuse, and injury. This project uses longitudinal data from the Baltimore Longitudinal Study of Aging (BLSA) and other studies to examine the influence of modifiable risk factors on the occurrence of premature deaths and unnecessary morbidity and disability. Identification of risk factors can lead to primary prevention efforts.